Catamaran 2 fat bikes into a Quad

Spidennis

Spidennis

This is a change of design from
I now have 2 identical fat bikes so I want to catamaran them together.
I have a bunch of 1” square aluminum tubing to frame them together.

My goal is to do a beach trip, 367 miles of Texas beach from Mexico to Louisiana with about a dozen water crossing along the way and to have sail assist. I will pedal, sail, and float the distance. My boat will be a pair of inflatable SUPs ( Stand Up Paddle Boards). Power for the boat will be pedal power, and sail.
I live and work on South Padre Island, Texas where I give sandcastle lessons on the beach, mostly during the summer when school is out. I use a bike/trike pulling a cart with my gear. I’ve been up and down the coast a lot of different ways , kayaked the entire way, used my jeep, motorcycle, sailboat but never did the entire beach in one trip. This quad is for this trip.
I’ll add some pics once I figure out how to do that.
 
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With a jackshaft between the bottom brackets for drive and a seat just above and behind that you could raise the steering to attach to the stems to get it away from where you want your pedals to be. You could use a beam where you have the wood across the tops of the seat posts to mount a steering wheel and run a rod to a similar bar mounted on the top of the head tubes with go-kart type steering actuating on the stems. Your sail mast can also be mounted from the beam across the seat posts putting the controls in easy reach.

7E8gHlL.jpg
 

Here shows a steering clearance concern, especially with 26” tires. I feel like I’m reinventing the wheel when many have already gone down this path but I can’t find anything about these past builds. What I have found with catamaran quads is mostly they use upright seating, a regular bike seat or a chair position, not a recumbent. Once I build this catamaran version I’ll go back to my original idea like in my first thread, I’ll know a lot more then.
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Spidennis said:
I am only 5’3” so….
And if I sit far enough back.
but then it cuts into my cargo area.
Click to expand...
I showed you my mock up , and my frames were 20" kids bike frames so shorter in height and length to yours:-

DSCF6429-sm-lines.jpg


The pedals are way out in front and the seat puts you sat to far back for my liking !
Also I judged this to hard to step over.
The easiest way to do this is ignore going recumbent and do an upright seating position , that way you can just step inside the frame and being almost vertical you feet won't collide with the front wheels when turning.
Just my $5 worth [ inflation you know ]
Paul
 
stormbird said:
I showed you my mock up , and my frames were 20" kids bike frames so shorter in height and length to yours:-

DSCF6429-sm-lines.jpg


The pedals are way out in front and the seat puts you sat to far back for my liking !
Also I judged this to hard to step over.
The easiest way to do this is ignore going recumbent and do an upright seating position , that way you can just step inside the frame and being almost vertical you feet won't collide with the front wheels when turning.
Just my $5 worth [ inflation you know ]
Paul
Click to expand...
We are definitely encountering the same characteristics in this design.
but being an expedition vehicle and not a regular daily driver I’d not mind a bit of effort getting into it. My butt really appreciates my recumbent seating in my terra trike Maverick as does my whole body. The upright vs recumbent position I can really feel is not just a comfort issue but an overall endurance factor. When going all day and everyday for a week both comfort and endurance are key components to success. Also the center of gravity is much lower so when I apply sail power I’ll have better stability and the boom has someplace to go. Granted the catamaran layout loses big points to a custom flat design like I originally intended as in my first thread for pretty much everything but this is quicker and I do have front wheel suspension and steering already figured out and done with the catamaran layout. My goal is a spring time launch date so I’m feeling the need to step up my efforts and time table.
 
Ok I understand a little especially the ' time pressure ' element so no more talk of mine , for different reasons to yours I deemed it a dead end.

Start with a boom as you have got in one of your pictures and do what I showed in mine.
Add pedals at the front of the boom and add your proposed seat at the correct distance [ copy other trikes dimensions ]
Then prop it up for the proposed pedal/seat height , strong enough to sit on.
You then are able to place the bikes either side and judge where the seat needs to be , don't forget you need some weight on the front wheels , especially if you plan carrying cargo behind it or towing a trailer

Paul
 
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to start out I think this will be one wheel drive to make it simple. The drive sprocket can be in a position where it will stay clean. I also have to experiment with the gearing to know what size sprockets to use and if this cassette will work. It would be nice to be able to shift but I’m thinking an internal geared hub might be useful.
 

Make the quad wider? I was trying to keep it so I can transport it in my van, but that is low priority, plus I can use my 4x8 trailer to do that.
First and foremost it’s an expedition vehicle, to travel 367 beach miles, and get thru to and from the launch and landings which is a really tough part and why I need 26” fat tires vs 20’s like a lot of trikes use.
I find I need to sit more forward, for better weight distribution and better cargo area, but the wheels when turning get in the way. So? Then move them out more. Make the quad wider. Ok, time to see how this looks.
 
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wider is better? I think so! This isn’t meant to run on the street but on the beach so size isn’t an issue. I can now sit forward so my weight is more one the front wheels for better weight distribution and the wheel can turn for steering. I also have more cargo area and that can be more centered too. Keeping the weight low is important, especially with a sail. Having a wider footprint will be more stable when sailing and having more personal room for sailing will be nice too. Since I am bolting it all together I’ll be able to disassemble it at the end of the trip for transport if necessary.
I used up the entire length of this heavy gauge aluminum square tubing just to see what the maximum size I can put together, and still be able to roll it out thru the double doors of the shop. I’m liking it!
 
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